Such a seat hinge mechanism is known from document FR2977205. However, in such a device, the spring which advantageously biases the drive shaft against an abutment, at a distance from the locking positions of the control cams in the hinge mechanisms, is external to the hinge mechanism itself.
The present invention is intended to improve seat hinge mechanisms, to render them more compact and more easily integrated while providing appropriate safety features and an impression of quality.